Probably some kind of sponge. Those are porifera which puts them in a different phylogenetic category than the one shared by both cows and comb jellies.
I asked ChatGPT to give me all the characteristics of a cow then asked for an animal that fitted the opposite of each characteristic. It's response was that an antlion larva is the opposite of a cow.
it has to be:
>animal
>invertebrate
>carnivore (cows probably can eat meat like most herbivores do, but it's probably rare)
>small
>no bilateral symmetry
>nuisance to humans
Jellyfish
Call regular NPCs who aren't exceptional mehjellyfish as opposed to lolcows.